structseq and keywords?

[Quinn Dunkan]

Is structseq supposed to take keyword args?  From the source I assume it was
meant to, but they're unused.

I suppose they'd interact poorly with sequence args, but I'd expect them to be
mutually exclusive:

ss(attr=bar) #-> attr set to bar, rest set to None
ss(a, b, c) #-> initialize with (a, b, c)


It also seems odd that structseq expects a single sequence rather than a
variable number of args.

I've been meaning to give python access to structseqs, since I think it would
be useful for python as well as C code.